Volume materials rendering weirdly
You have a few instances of overlapping faces, and some cylinders directly above other cylinders with faces touching or overlapping.

You also have a few instances of objects inside objects.

Depending on your volume material settings that can lead to artifacts, and in general Blender doesn't like it, confusing the rendering engine on how to calculate depth and render the volume materials.

Overall your scene might benefit from some optimization. Since all cylinders seem to be roughly the same shape you don't need so many unique mesh data. You could probably make them all instances of the same object and simply scale them differently in the Z axis.

This will make your workflow easir if you ever need to edit the shape of the cylinders, and also make your scene lighter and faster to render since there's less unique geometry to upload into memory.

Also make sure you apply materials by object (as opposed to by data) right next to the material name dropdown menu, so each instance can have it's own material definitions